1. Field of the Invention
This invention relates to an altitude compensation apparatus for a carburetor to be connected to the main body of a bleed air compensation apparatus which includes passages having set throttles and communicated with a primary main air bleed port and a slow air bleed port disposed in the fuel passage of the carburetor of a car engine, and bellows containing air so that additional bleed air is supplied to cope with the lean air at high altitudes. More particularly, the present invention relates to an altitude compensation apparatus for a carburetor having a construction in which operation rods are fitted to the bellows of the main body of said compensation apparatus; a plurality of flow rate control valves are opened and closed by a vacuum corresponding to the altitude; the passage is opened and closed by the flow rate control valves; and thermosensitive operation valves for sensing when the engine is cold and after it has warmed up are interposed in auxiliary passages branched from the passage so as to ensure an increased air bleed quantity in driving with the engine being yet cold.
2. Description of the Prior Art
As is well known, a car is very mobile and can move from low altitudes such as along coastal regions to high altitudes such as in the mountains. Hence, the air density in the air-fuel mixture supplied by a carburetor to the engine is likely to become rich due to the pressure change when the car moves from low to high altitudes. In other words, the air-fuel ratio becomes lower in the highlands than in the lowlands.
Accordingly, an altitude compensation apparatus is generally disposed in order to provide a constant air-fuel ratio and ensure stable engine operation irrespective of the altitude difference (pressure difference).
The conventional altitude compensation apparatus 1 will be briefly described with reference to FIG. 1. The bellows 2, into which the set reference atmospheric pressure is sealed, are disposed inside the casing 4 of the main body of the compensation apparatus and detect the pressure change due to the altitude difference. The bellows 2 contract at low altitudes and a fixed valve 6 which is integral with the bellows closes a bleed port 5, thereby cutting off the air from an air filter 7. Accordingly, the bleed air is not delivered to passages 16 and 17 that have fixed throttles 14 and 15 and are communicated with a primary main air bleed 10 of the fuel passage 9 of the carburetor 8, a primary main air bleed port 12 of a slow air bleed port 11, and a slow air bleed port 13 so that the air-fuel mixture is distributed at a set air-fuel ratio to each cylinder via an intake manifold 18. In high altitudes, on the other hand, the bellows 2 expands and the fixed valve 6 opens the bleed port 5 so that air from the air filter 7 is delivered to the primary main air bleed port 10 and the slow air bleed port 11 through the passages 16 and 17. Thus, the quantity of bleed air is increased from that in low altitudes while the quantity of fuel is decreased, thereby preventing the air-fuel ratio from becoming over-rich in at high altitudes.
In the conventional altitude compensation apparatus 1 described above, however, the throttles 14 and 15 are disposed in such a manner that the quantity of bleed air is controlled in accordance with the pressure difference resulting from the altitude difference, irrespective of the engine temperature. Accordingly, if the engine operates suitably after it is warmed-up, the quantity of bleed air is likely to be insufficient when the engine is cold because the choke is cold, the air-fuel ratio is too rich and the like. Especially when the engine is cold at higher altitudes, the air-fuel ratio is most likely to be too rich so that driving performance deteriorates, and the exhaust gas is insufficiently processed and purified.